This invention addresses the need to characterize particles within harsh environments. It was initially inspired by the need to quantify particle ingestion by an aircraft gas turbine engine employed in an aircraft. Such aircraft are increasingly being called upon to operate in harsh environments, particularly those with a significant presence of sand and dust. Ingestion of sand and dust by a gas turbine engine can result in erosion of hardware, clogging of passageways, and deterioration of cooling systems. This leads to degradation of the engine's performance and ultimately could lead to engine failure. Engine manufacturers and customers would prefer to implement real-time health monitoring to detect airborne sand/dust and its penetration into the core of the engine where the most substantial damage can occur. Available particle measurement systems are not rugged enough to be applied to the harsh environment encountered within a gas turbine engine. Such a harsh environment may have extreme temperatures ranging from −100° F. (−73° C.) to 570° F. (300° C.) or more and pressure ranging from 0 psia (0 MPa) to 250 psia (1.7 MPa) or more. A traditional particle measurement system, for example, an optical particle sensor with integrated laser source and detector electronics, would likely not survive or function properly under such extreme conditions. Also, as the government imposes ever more stringent regulations regarding the emission of particulate matter (PM) by engines, the monitoring of those emissions becomes paramount.
The use of optical scattering methods for particle characterization has been repeatedly demonstrated for applications such as contamination monitoring in clean facilities, pharmaceutical and food preparation, indication of indoor air quality, and the monitoring of environmental pollution caused by industrial and vehicular emissions, biomass burning, volcanic activity, and dust upheaval by wind and vehicles. These methods are applied in relatively benign environments where temperature and pressure do not differ significantly from atmospheric conditions. Particle measurement systems employing these methods typically integrate the sensing probe components and electronic processing and control components into one unit. As such, the more delicate components of the particle measurement system cannot generally survive in harsh environments. Also, most particle measurement systems use electrical signals and near a harsh environment these signals are prone to electromagnetic interference (EMI) effects.
Accordingly, the present disclosure is directed to a novel sensing methodology that addresses the aforementioned deficits. More specifically, the present disclosure is directed to a particle measurement system that includes one or more sensor probes interconnected via optical fibers or cables to one or more isolated electronic units to detect dust particles and/or debris within an engine such as a gas turbine engine. By splitting passive optical components from temperature (and condition) sensitive components, such as the laser(s) and electronics within the electronics unit, only the sensor probe components are exposed to the harsh environment. Also, since optical fibers are used to interconnect the sensor probe and electronics unit the system is also more resistant to EMI effects. To survive the harsh environment the sensor probe is typically a sealed unit and, as such, can be used in both gaseous and liquid environments.